Method and apparatus for manufacturing inner tubes



July 1, 1941. l D.' J. HINMAN 2,423,147

METHOD AND` APPARATUS FOR MANUFACTURNG INNER 'I-UBES Filed Dec. 9, 1944 3 Sheets-sheet 1 ATTORNEY July 1, 1947. D. J. Hmmml 2,423,147

METHOD AND APPARATUS FOR MANUFACTURING INNER'TUBES Filed Dec. 9, 1944 5 Sheets-Sheet 2 July 1, 1947.

D. J. HINMAN METHOD AND APPARATUS FOR MANUFACTURING INNER TUBES Filed Dec. 9, 1944 INVENTOR. 005/? //V/VA/V ATTORNEY Patented July 1, 1947 `UNITED STATES PATENT OFFICE Application December 9, i944, seriaiNo. 561332 11 Claims.

This invention relates to a method and apparatus for manufacturing inner tubes for pneumatic tires and in `particular it relates to means for handling and conveying inner tube stock prior to its assembly in the form of a completed annulus. p

The conventional method of manufacturing inner tubes consisted of extruding inner tube stock to a shape conforming to a circular outline of the inner tube in cross section. In Athis condition the tubular stock Was extruded in a continuous straight length. Thereafter the tube was cut to proper length and the ends were spliced to form a completed annulus. Directly after the tubular stock was extruded the tube collapsed so that the opposing inner Walls of the tube lie in adjacent relationship.

Prior to vulcanization of inner tubes it is necessary to inflate the Atube to substantially its normal vulcanized shape. Since ination of the tube which is now in the shapeV of an annulus takes place While the rubber stock is in a raw state, the wall of the stock becomes varied due to stretching and compression of the rubber composition. The unvulcanized tube in its uninflated condition is substantially in circular band form as compared with its ultimate inflated annular shape. When air is introduced into an inner tube While in its band state so as to 'convert it cross sectionally into an annular form, it is obvious that a Wide difierential occurs in the perimeter of the inner tube at the rim circumference as compared with the tread circumference. This thinning-out of the Wall of the tube in the tread region is objectionable in that it leads to premature failure of the tube. There is presently a tendency toward larger cross sectional inner tubes having smaller rim diameters. Under such circumstances the differential between rim and tread perimeters is greatly increased with the result that the thinning out of the tube Wall on such inner tubes becomes extremely objectionable.

It has been proposed in some cases to overcome this condition by maintaining extruding dies in such a relationship that the tread portion of the inner tube would result in a heavier Wall than the remaining portion of the tube. This, vhovvever, was not found satisfactory because greater pressureswererequired to inflate the raw tube properly and in many case localized thinning out of the Wall of the tube in the region of the tread becameA prevalent. Also it was extremely diiiicult to maintain luniformity of thickness of the tube wall.

l, In accordancewith the present invention, I ex- `trude` inner Y tube' stockH and bendjthe freshly formed vtubejto an ar'of the desirediradiusland maintain the tube inithisrarcuate condition while advancing'it` along a more or less serpentine path so as to cause the tube to assume permanently the approximate curvation of the finished inner tube. i The nature of the serpentinepath along 'Which the tube stockisadvanced is important and preferably isformed by providing a number of power drivenrrollerslin rows disposed at each side of a central vertical' plane sothat the Atube can `be laced Vor draped back` and forth-'between the'successive rollersfto sag therebetween in connected arcs of the desired curvation. i The side walls of the tube arepreferablycollapsed flat or nearly iiatatthistime.` i -i i Thetube is handled in this manner by? conveying the tubestock from the extruder overfa plurality of [drivenv frustrosconical supporting Vrollers 20 disposed at opposite sides of a central vertical piane.V The inner tubestock' is cooled while 4it is y advanced along this approximate serpentine pa'th vby the rollers;whereupon-'the 'rubber stool; becomes suciently rigid to permit handling without undue 'distortion'.` i i i i l l Byjthis'arrangementvtherimland tread portion fof the Wallseoffth inner tube become fixed' in their raw state so that'littlefor-no' expansion or compressionisL required when'the inner `tube' is inflated to normal size-.AFAS a result vof this operation anfinner tube-is formed finwhich'the walls ofthe tube aresubstantially uniformthroughout, for while the tube is bent upon'leaving the"ex truder sothatone curved Wall vWill be longer than the other, the thickness'ilofthe `walls of the .tube isifound in `practice to'be uniform for all practical purposes. Apparently the' stock upon leaving the extrud'er flows slightly faster at the outsideV of the" bend 'of Athe tube than at the inside of `the tube bend to automaticallyuequalize the thickness of these walls l r l Among the objects of .myf inventionare to provide an inner tubevhaving a substantially uniform wall thickness; 'to provide means for handling and maintaining ravv` tube-stock' in a more or less serpentine formation; to provide Va l. continuous Vmetlfiodrof extrudinginneritube stock and advancing it alngf` a `more l' ori less serpentine L path; to provide conveying means for.- advancingttube. stock along an approximate serpentine path and having associate-means on which the stock may be measured and cut to proper length to form'units capable of being spliced into a completed '..annulus; and to provide an eliicient and economical apparatus for-manufacturingtubes as stated.. il;

These and other objects and advantages will appear more fully in the following detailed description when considered in connection with the accompanying drawings illustrating one good practical embodiment f the invention.

In the drawings:

Fig. 1 is a top plan View of apparatus embodying the features of my invention;

Fig. 2 is a side elevational view thereof; and

Fig. 3 is a transverse view in section, taken along lines 3-3 of Fig. 1.

With reference to the drawings, and in particular to Figs. l and 2, I show an embodiment of my invention comprising, npart, a structural frame I sup-porting a plurality of driven frustreconical rollers 2. The frustro-ccnical rollers are positioned in rows on opposite sides of a vertical central plane in relation to a conventional inner tub-e extruding head 3 so that the distance between the center of the extruding head and the upper surface of the frustro-conical rollers is substantially equal to the desired radius of the inner tube. When different diameter tubes are desired it is necessary to vary the distance between the extruder head and the frustro-conical rollers. This is accomplished b-y means of hand wheels Il located one at each leg of the frame I and communicated in complementary threaded relationship with a leg extension member 5. By this provision of manual operation of the hand wheels 4 and associated threaded extension members, the height of the frame may be adjusted in relation to the tuber.

The upper portion of the frame I is provided with the horizontally disposed angle rail 6 at each` side of the frame. The angle rails as shown in Fig. 3, are positioned to support the frustreconical rollers 2 so that their axes lie in a path radially of the central longitudinal axis for the arcuate path of the extruded .tubular stock S.

AEach of the frustro-conical rollers is supported by a shaft 1 mounted in a bearing block 8 bolted to the anglel rail 6, The frustro-conical rollers are located at spaced intervals along the length of the angle rails 6, and are spaced at equal intervalsY along each rail but are located in an intermediate position relative to the diametrically opposed set of frustro-conical rollers.

rihroughout ther conveying operation it is necessary to drive each ofl the frustro-conical rollers so as to prevent any undue stretch or distortion in the unvulcanized tube. A motor S and reduction unit I positioned on a cross member II forming a part of the frame I provides a drive for the rollers 2. A shaft I2 extending towards each side of the frame from the reduction unit I0 ha-s upon each of its ends a universal joint I3 that drives a sprocket I4 supported by a bracket I5 mounted on the cross member Il. This drive sprocket serves to drive a chain I6 that engages with a sprocket I1 keyed to the shaft 1 which supports a roller 2. Thel same chain l5 engages with similar sprockets I1 for the other rollers 2 along one side of the frame I.

Between each second roller 2 is an idler sprocket I8 which serves to maintain the chain I6 in proper meshing engagement with the sprockets I1. Idler sprockets I9 and 20 supported by the angle rail 6 complete the path for the chain I6. A similar set of chain andsprockets driven from the same motor 9 is located on the opposite side of the frame I for driving the opposite set of rollers 2.

Extending between the angle rai-ls, 6 is an arcuate pan 2l. The side edges of this pan are attached, as by welding, to the rails 6, and its shape is such as to provide clearance for the inner tube in its arcuate path through the conveying apparatus. The end plates 22 form an enclosure with the bottom portion of the pan 2l. The purpose of the pan is to provide means for collecting the water which has been sprayed onto the tube stocks while moving through the conveying apparatus. A drain pipe 23 located at the bottom of the pan permits removal of Water collected in the pan.

As the extruded tube leaves the tuber head 3 the rubber composition is relatively hot and consequently is soft and easily distortable. In order to set the rubber to a harder state so that it will withstand a reasonable amount of handling without distortion it is necessary to cool the rubber stock after it leaves the tuber. To accomplish this cold water is sprayed onto the exterior of the tube as it moves progressively through the conveying apparatus.

A water conduit 24 extends within the pan along its length. A number of nozzles 25 are positioned at spaced intervals along the conduit Ell so that a spray of water may be directed against each face of the exterior walls of the inner tube stock. When the tube stock reaches the end of its path over .the conveying 'apparatus it is sueiently cooled and set for subsequent manual handling. At the end of the conveyor is a compressed air conduit 26 adapted to direct a stream of air from small apertures in the conduit against the surface of .the tube so as to remove excess water from the tube.

After the tube stock leaves the conveying ap,- paratus the stock moves onto a horizontally disposed rotatable table 21. An idler conical roller 28 supported from the frame I by a bracket 29 operates to guide the tube stock onto the table 21. In some cases the roller 28 may be driven.

As shown in Figs. 2 and 3, the table 21 is driven from th'e motor 9 by a sprocket 30 mounted on the shaft I2 extending from the reduction unit I0. A chain 3l engaging with the sprocket 30 and a sprocket 32 operates to drive a reduction unit 33 which in turn rotates the table 21. The structural frame 34 extending from the main frame I provides a support for the reduction unit 33.

In the operation of the apparatus the conventional tuber 3 is started on its extrusion process and the tube stock S is manually carried up over the first frustro-conical roller 2. Thereafter tli'e end of the tube stock is draped or laced back and forth over alternate rollers 2 until it passesv com.- pletely through the conveying apparatus. Although the tube stock begins to take a curved path as soon as it leaves the tuber die it is found that it is not necessary to make any change in the tuber die head from its uniform symmetrical construction.

The fact that the tube stock is moved upwardly as it leaves the tuber die head apparently operates automatically to extrude the rubber stock faster at the lowermost portion of the die. This automatically takes care of the uniform thickness in the wall of the tube in both the rim and tread region of the tube.

In order to maintain the shape oi the tube and to prevent it from otherwise wrinkling asv it moves over the supporting rollers 2 it has been found necessary to inflate. partially, the tube during its cycle of operation. Inflation of the tube is, produced by means of a conduit 35 leading from a source of compressed air and which enters the die head and supplies compressed air to inilate the tube directly as the tube is extruded. This partial inflation of the tube prevents a meeting of adjacent walls of the tube and in this way the tube is better adapted to adjust itself as it moves over the supporting rolls. Soapstone is preferably injected into the tube to prevent adh'esion between the tube walls, this may be done by forcing it into the tube through a central longitudinal passage in the tuber screw.

When the tube reaches the end of the conveying apparatus it passes around the guide roller 28 and lies in a flat and arcuate position on top of the rotating table l2?. Since the movement of the stock is relatively slow an operator has ample time to cut the-tube at a point such as at 36 and remove the cut tube to a belt conveyor or some other position for subsequent operation. .l l It will be seen from the. foregoing that by advancing` the freshly extruded tube from one driven roller to another disposed at opposite sides of a vertical central plane, the tube may be draped between the rollers in arcs of the desired curvature. In this manner the weight of the tube between spaced rollers is utilized to cause it to drape or sag in the desired arcuate curvature as it is advanced along an approximate serpentine path.

While I have shown and described a preferred embodiment of my invention it is to be understood that the apparatus and method are susceptible of obvious modifications all of which I contemplate Within the spirit of the invention and the scope of the appended claims.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

l. The method of manufacturing inner tubes comprising the steps, extruding inner tube stock in the form of a continuous tubular length', conveying the length of extruded stock in an approximate serpentine formation so as to maintain the tube in the form of an arcuate curve by suspending it in draped loops from successive points disposed at opposite sides of a vertical plane and advancing the tube past said points, and cutting the stock in unit lengths to form a completed annulus substantially free of stresses at the rim and tread region of the tube upon innat-ion sufficient to form a torus.

2. The method of manufacturing inner tubes comprising the steps, extruding inner tube stock in the form of a continuous tubular length, conveying the lengthl of extruded stock in an approximate serpentine formation so as to maintain the tube in the form of an arcuate curve by suspending it in draped loops from successive points disposed at opposite sides of a vertical plane and advancing the tube past said points, cooling the stock while being conveyed, and cutting the stock in unit lengths to form a completed annulus substantially free of stresses at the rim and tread region of the tube upon inflation suincient to form a torus.

3. The method of manufacturing inner tubes comprising the steps, extruding inner tube stock in the form of a continuous tubular length, conveying the length of extruded stock in an approximate serpentine formation so as to maintain the i tube in the form of an arcuate curve by suspending it in draped loops from successive points disposed at opposite sides of a vertical plane and advancing the tube past said points, maintaining the tubular length of stock in a partially inflated state while being conveyed, and cutting the stock in unit lengths to form a completed annulus substantially free of stresses at the rim and tread region of the tube upon inflation sufcient to forni a'torus. y i f 4. The method of manufacturing inner tubes comprising the steps, extruding inner tube stock inthe form of a continuous tubular length, conveying the lengthof extruded stock in an approximate serpentine formation so as to maintain the tube in the form of an arcuate curve by suspending it in draped loops from successive points disposed at opposite sides of a vertical plane and advancing the tube past said points, cooling the stock while being conveyed, maintaining the tubular length of stock in a partially inflated state while being conveyed, and cutting the stock in unit lengths to form a completed annulus sub- -stantially free of stresses at the rim and tread region of the tube upon inflation sufficient to form a torus. i

5. The method of producing curved tubular stock of plastic composition comprising the steps, continuously extruding a tube of the stock, and advancing the freshly extruded tube in a draped condition from one side to the other across a vertical plane along an approximate serpentine path' so as to impart to the tube an arcuate contour that will cause'it to assume readily the shape of an annulus.

6. The method of producing curved tubular stock of uncured rplastic composition comprising the steps, continuously extruding a tube of the hot stock and imparting thereto an arcuate curvature, advancing this freshly extruded tube along an approximate serpentine path so that it travels back and forth in sagging loops that intersect a vertical plane and retains this arcuate curvature as it travels along said path, and cooling th'e tube as it travels along lsaid path.

'7. The method of producing curved tubular stock of plastic composition comprising the steps, continuously extruding a tube of the stock, and advancing the extruded stock in an approximate serpentine path back and forth over successive supports at points substantially diametrically opposed so that the stock travels indirectly in a longitudinal direction and sags in arcs that extend transversely to said longitudinal direction between the opposite supports, to thereby produce a change in the length of opposite walls of the tube and impart to the tube an inherent arcuate contour.

8. An apparatus for manufacturing inner tubes comprising, a tuber for extruding inner tube stock, and means associated with the tuber for supporting and advancing the tuber stock along an approximate serpentine path while maintaining the tube in an arcuate condition, including stock supporting rollers disposed along a zigzag path so that the axes of these rollers intersect a central vertical plane and the rollers serve to .support and advance the stock in successive arcs draped back and forth across said plane from one roller to another.

9. An apparatus for manufacturing inner tubes comprising, a tuber for extruding inner tube stock, and means associated with the tuber for supporting and conveying the tuber stock while maintaining the stock in an arcuate and somewhat serpentine formation, including stock supporting tapered rollers disposed in rows on opposite sides of a central vertical plane, and means for driving these rolls to advance the stock back and forth across said plane in draped loops between the rollers.

10. An apparatus for manufacturing inner tubes comprising, a tuber for extruding inner tube stock, and means associated with the tuber for supporting and advancing the tuber stock along an approximate serpentine path while maintaining the tube in an arcuate condition, including stock supporting rollers disposed in rows on opposite sides `of a central vertical plane to support and advance the stock in successive arcs draped between the rollers across said plane, means for driving said rollers, and means at the tuber for inating the tuber stock.

11. The method of manufacturing inner tubes comprising the steps, extruding inner tube stock in: the form of a, continuous tubular length, conveying the` length' of extruded stock in an approximate serpentine formation so as to maintain the tube in the form of an arcuate curve having the radius. of the finished inner tube. by suspending it in draped loops from successive points disposed at opposite sides of a, Vertical plane and advancing the tube past said points, to thereby impart to this tube an inherent arcuate contour correspond-ing to that of the nished inner tube.

DORR J. HINMAN.

REFERENCES CITED The following references are of record in the lo le of thisv patent:

UNITED' STATES PATENTS 

